A randomized placebo-controlled clinical trial is proposed to test the efficacy of dietary supplements of two forms of polyunsaturated fatty acids (PUFA) and of potassium in reducing blood pressure among persons with mild hypertension. Recently, in a double-blind trial, the Applicant and colleagues observed that 23g per day of linoleic acid, a polyunsaturated fat, but not oleic acid, a monounsaturated fat, significantly lowered blood pressure in normotensives. Other investigators have reported modest hypotensive effects of linoleic acid and of potassium administered separately. Controlled trials of fatty acids with and without potassium in hypertensive patients are needed. Forty patients with mild hypertension will be treated with the following therapies: 1) linoleic acid 12g/day and 24g/day, 2) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), polyunsaturated fatty acids concentrated from fish oil, 3g/day and 6g/day, 3) a combination of potassium and each of the two classes of PUFA, 4) chlorthalidone 25mg/day, 5) placebo. Each subject will be tested in random sequence for six two-month periods composed of three diet regimens, two placebo intervals, and a period of treatment with chlorthlidone. The study design and sample size provides a power of over 90% to detect a significant 3mm Hg difference in mean BP between any two of the treatments or placebo. At the conclusion of the trial, the best dietary regimen will be selected for a long-term clinic based study. The dietary therapy will be compared with standard drug therapy for amount of blood pressure reduction, incidence of side effects, patient acceptability, and plasma lipoprotein levels in a one-year randomized trial. The results will be analyzed on an intention-to-treat basis as compared to the clinical efficacy model planned for the initial protocol. The discovery of a satisfactory dietary supplement to treat mild hypertension would be of great interest and practical importance.